Primordial and asymptotic inflation in Brans-Dicke cosmology

TL;DR

This paper explores how Brans-Dicke cosmology can simultaneously explain primordial and late-time inflation, linking their ratio to the Brans-Dicke parameter and aligning predictions with recent measurements.

Contribution

It demonstrates that Brans-Dicke theory can account for both early and late inflationary phases with a specific relation to the parameter , and predicts the future Hubble parameter consistent with observations.

Findings

The ratio of primordial to late-time inflation is proportional to .

Predicted future Hubble parameter is 0.86 times the current value.

Variation of G is consistent with recent measurements.

Abstract

The basic motivation of this work is to attempt to explain the rapid primordial inflation and the observed slow late-time inflation by using the Brans-Dicke theory of gravity. We show that the ratio of these two inflation parameters is proportional to the square root of the Brans-Dicke parameter $% \omega$ $(\omega\gg1) $. We also calculate the Hubble parameter $% H$ and the time variation of the time dependent Newtonian gravitational constant $G$ for both regimes. The variation of the Hubble parameter predicted by Brans-Dicke cosmology is shown to be consistent with recent measurements: The value of $H$ in the late-time future is predicted as 0.86 times the present value of $H$.